熱處理對于有高硬度、高耐磨性和高韌性要求的塑料模具,表面熱處理廠家要選用滲碳鋼來制造,并把滲碳、淬火和低溫回火作為最終熱處理,表面熱處理廠家對滲(shen)碳(tan)(tan)層(ceng)(ceng)的要(yao)求(qiu),一般(ban)滲(shen)碳(tan)(tan)層(ceng)(ceng)的厚度(du)為(wei)o.8—1.5mm,當壓制含硬質填料的塑料時(shi),模具(ju)滲(shen)碳(tan)(tan)層(ceng)(ceng)厚度(du)要(yao)求(qiu)為(wei)1.3~15mm,壓制軟性塑料時(shi)滲(shen)碳(tan)(tan)層(ceng)(ceng)厚度(du)為(wei)0.8~1.2mm。滲(shen)碳(tan)(tan)層(ceng)(ceng)的碳(tan)(tan)含量為(wei)0.7%~1.0%為(wei)佳。若采用(yong)碳(tan)(tan)氮共滲(shen),則耐磨性、耐腐蝕性、抗氧化、防粘性就(jiu)更好。
滲(shen)(shen)碳(tan)溫度(du)(du)(du)一般在900—920攝(she)氏度(du)(du)(du)之間,復(fu)雜型(xing)腔的(de)小型(xing)模具(ju)(模具(ju)鋼)可取(qu)840—860攝(she)氏度(du)(du)(du)中溫碳(tan)氮共滲(shen)(shen)。滲(shen)(shen)碳(tan)保溫時(shi)間為1~l0h.具(ju)體(ti)應根據對(dui)滲(shen)(shen)層厚度(du)(du)(du)的(de)要求來選擇。滲(shen)(shen)碳(tan)工藝以采用分(fen)級滲(shen)(shen)碳(tan)工藝為宜(yi),即高溫階(jie)段(900—920攝(she)氏度(du)(du)(du))以快速將碳(tan)滲(shen)(shen)入(ru)零件表(biao)層為主.中溫階(jie)段(820~840攝(she)氏度(du)(du)(du))以增加滲(shen)(shen)碳(tan)層厚度(du)(du)(du)為主,這樣在滲(shen)(shen)碳(tan)層內建(jian)立(li)均勻合理的(de)碳(tan)濃度(du)(du)(du)梯度(du)(du)(du)分(fen)布,便(bian)于直接淬火。
提(ti)高韌(ren)性的(de)(de)(de)球墨(mo)鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)退火(huo)球墨(mo)鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)在鑄(zhu)(zhu)(zhu)造過(guo)程中此普通灰(hui)口鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)的(de)(de)(de)白口傾向大,內(nei)應力也較大,鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)件(jian)(jian)(jian)(jian)很(hen)難(nan)得到(dao)(dao)純粹的(de)(de)(de)鐵(tie)(tie)(tie)素(su)(su)體(ti)(ti)(ti)(ti)(ti)(ti)或珠光(guang)(guang)(guang)體(ti)(ti)(ti)(ti)(ti)(ti)基(ji)體(ti)(ti)(ti)(ti)(ti)(ti),為(wei)(wei)提(ti)高鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)件(jian)(jian)(jian)(jian)的(de)(de)(de)延性或韌(ren)性,常(chang)將鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)件(jian)(jian)(jian)(jian)重(zhong)新(xin)加(jia)熱(re)到(dao)(dao)900-950℃并保溫(wen)足夠時(shi)間(jian)進(jin)行高溫(wen)退火(huo),再爐(lu)冷(leng)(leng)到(dao)(dao)600℃出(chu)爐(lu)變(bian)冷(leng)(leng)。若鑄(zhu)(zhu)(zhu)態組織由(鐵(tie)(tie)(tie)素(su)(su)體(ti)(ti)(ti)(ti)(ti)(ti)+珠光(guang)(guang)(guang)體(ti)(ti)(ti)(ti)(ti)(ti))基(ji)體(ti)(ti)(ti)(ti)(ti)(ti),以及球狀(zhuang)石(shi)墨(mo)組成,為(wei)(wei)提(ti)高韌(ren)性,只需將珠光(guang)(guang)(guang)體(ti)(ti)(ti)(ti)(ti)(ti)中滲碳(tan)體(ti)(ti)(ti)(ti)(ti)(ti)分解轉(zhuan)換(huan)為(wei)(wei)鐵(tie)(tie)(tie)素(su)(su)體(ti)(ti)(ti)(ti)(ti)(ti)及球狀(zhuang)石(shi)墨(mo),為(wei)(wei)此將鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)件(jian)(jian)(jian)(jian)重(zhong)新(xin)加(jia)熱(re)到(dao)(dao)700-760℃的(de)(de)(de)共析(xi)溫(wen)度(du)(du)上(shang)下經(jing)保溫(wen)后爐(lu)冷(leng)(leng)至(zhi)600℃出(chu)爐(lu)變(bian)冷(leng)(leng)。工(gong)藝(yi)過(guo)程是將基(ji)體(ti)(ti)(ti)(ti)(ti)(ti)為(wei)(wei)鐵(tie)(tie)(tie)素(su)(su)體(ti)(ti)(ti)(ti)(ti)(ti)及珠光(guang)(guang)(guang)體(ti)(ti)(ti)(ti)(ti)(ti)的(de)(de)(de)球墨(mo)鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)件(jian)(jian)(jian)(jian)重(zhong)新(xin)加(jia)熱(re)到(dao)(dao)850-900℃溫(wen)度(du)(du),原鐵(tie)(tie)(tie)素(su)(su)體(ti)(ti)(ti)(ti)(ti)(ti)及珠光(guang)(guang)(guang)體(ti)(ti)(ti)(ti)(ti)(ti)轉(zhuan)換(huan)為(wei)(wei)奧(ao)(ao)氏(shi)體(ti)(ti)(ti)(ti)(ti)(ti),并有部分球狀(zhuang)石(shi)墨(mo)溶(rong)解于(yu)奧(ao)(ao)氏(shi)體(ti)(ti)(ti)(ti)(ti)(ti),經(jing)保溫(wen)后空(kong)冷(leng)(leng)奧(ao)(ao)氏(shi)體(ti)(ti)(ti)(ti)(ti)(ti)轉(zhuan)變(bian)為(wei)(wei)細珠光(guang)(guang)(guang)體(ti)(ti)(ti)(ti)(ti)(ti),因此鑄(zhu)(zhu)(zhu)件(jian)(jian)(jian)(jian)的(de)(de)(de)強度(du)(du)提(ti)高。